H.sub.2 receptor antagonists, anti-choline agents, gastric mucous membrane-protecting agents and antacids are now mainly used as anti-ulcer agents. Although these agents have medicinal effects, undesirable adverse side effects are also found. For example, the H.sub.2 receptor antagonists most frequently used at the present are excellent in the action of controlling a secretion of gastric juice, but are defective in that, after discontinuation of the administration, a counteraction of promoting a secretion of gastic juice appears. Anti-choline agents often show an excessive action of controlling a secretion of gastric juice because they have a parasympatholytic action, and moreover, they blunt the activity of the stomach and impair digestion. Since antacids temporarily neutralize gastric acid, they show a counteraction of promoting a secretion of gastric juice and other various adverse side effects. In short, an agent having excellent anti-ulcer action and showing no adverse side effects has not been developed.